The present invention relates generally to oceanic anti-biofouling and more particularly, but not exclusively, to retrofit hydrolization of seawater for production of halogen biocides in situ.
For over 30 years chlorine generation has been used by the swimming pool industry to keep pool water free of algae. A patent (U.S. Pat. No. 4,097,356) for such use was granted in 1978 with many granted since on chlorine generation. The use of generation over chlorine tablets is preferred in pools used year round, in salt water swimming pools and in marine animal rescue pods. A representative system for swimming pools provides a platinum-electroded cell in a recirculating system of the pool. Hydrolization of the recirculating pool water is turned on for a variable percentage of the time that recirculation occurs, the variation depending upon a number of factors including the temperature of the water, its pH and the bacterial load that the pool is under. For example, for a 10,000-gallon pool, the pump may recirculate pool water for eight hours a day with the hydrolization active for four hours, and consume about 36 watts. Fresh water pools require the addition of three parts per thousand (ppt) NaCl to operate; seawater pools generally require the same cycle time and chlorine levels as fresh water pools.
There are many organizations that use marine animal rescue pods for the recovery of injured marine animals to bring them back to their facilities. Some of these are located in tropical locations, e.g., on the Gulf of Mexico, which places a considerable bacteria and algae load on marine systems. There exist 36-watt chlorine generation systems that are able to manage the growth of marine organisms in various pod capacities, for example, 15,000 go 30,000-gallon pods.
Most manufacturers of oceanographic conductivity-temperature and depth (CTD) instruments employ some form of anti-biofouling device or technique. Some manufacturers are known to use copper mesh at an inlet to the sensors. Others use an anti-biofouling kit which is installed near the sensors of equipment probes for protection against biofouling. Still others use a chlorine generator pumped and cycled by their computer-controlled sampling system, which can provide 3-months protection on a Gulf of Mexico 3 meter buoy. Another solution sometimes used is provision of an anti-fouling toxic coating, Tributyltin (TBTO), within their conductivity sensors to ward off biofouling. It is common to be able to collect good data for 3-6 months before maintenance is necessary, although sediment can be a problem earlier.
The existing systems are generally capable of combating biofouling, when the system is designed with an in situ integral component. However, for systems which do not have a built-in anti-biofouling component, typical solutions include containment of the sensor within an enclosure.
Further, many existing systems generate, by some measure, too much biocide that can cause concern for disturbing the habitat in which the system operates. The systems essentially “flood” an area around the sensor with biocide to implement the anti-biofouling function. The biocide, not being targeted, must be generated in greater quantity. The generation of more quantity of non-targeted biocide, when the biocide is generated from an onboard power source, means that the power source is exhausted more quickly than would be the case if a more targeted, less quantity, biocide were produced.
What is needed is a retrofit hydrolization of seawater for production of directed and targeted halogen biocides in situ.